Electron microprobe dating and thermobarometry of Neoproterozoic metamorphic events in the Kekem area, Central African Fold Belt of Cameroon

Pan-African metamorphic evolution in the southern Yaounde Group (Oubanguide Complex, Cameroon) as revealed by EMP-monazite dating and thermobarometry of garnet metapelites

“…The BSE-imaging and analytical profiles revealed no distinct zonations in graytones and corresponding larger variations in Th contents within the grains. When the corresponding Th-U-Pb ages are considered, there are no indications of distinguishable multiple monazite age generations within a sample and when several samples are compared, as it has been described from other metamorphic domains (Schulz et al, 2007b;Tchato et al, 2009). The monazites apparently crystallized during a single metamorphism or thermal event.…”

“…These large NE-striking transcurrent faults are regarded as possible prolongations of the major shear zones of NE Brazil in a pre-drift Gondwana reconstruction (Castaing et al, 1994;Njonfang et al, 2008). The northern domain consists of high-grade gneisses (Tchato et al, 2009), intruded by widespread Neoproterozoic syntectonic plutonic rocks of high-K calc-alkaline affinities (Nguiessi et al, 1997;Nzenti et al, 1994Nzenti et al, , 2006Tagne Kamga et al, 1999;Nzolang et al, 2003;Djouka-Fonkwe et al, 2008;Kwékam et al, 2010;Njanko et al, 2010). The southern domain comprises Neoproterozoic lithostructural units of metasedimentary rocks, such as the Yaounde, Lom, Dja and Yokadouma Groups (Owona et al, 2003;Owona, 2008).…”

Paleo- and Neoproterozoic magmatic and tectonometamorphic evolution of the Isla Cristalina de Rivera (Nico Pérez Terrane, Uruguay)

“…New monazite can crystallize during younger events, especially when fluids enter the rock. This potential of the Th-U-Pb monazite EMP dating method to constrain several events has been repeatedly demonstrated, enclosing the age evaluation of shear zone deformation (Cocherie and Albarede 2001;Williams et al 2006Williams et al , 2007Tchato et al 2009;Just et al 2010;Schulz and von Raumer 2011). Furthermore, the K-Ar isotopic system allows one to establish the metamorphic cooling history from high to medium temperatures, beginning with cooling ages of amphibole (at *500°C) to muscovite at (*410°C; Blanckenburg et al (1989) or at *350 ± 50°C, Purdy and Jäger 1976;McDougall and Harrison (1999); to biotite at *310 ± 40°C (Grove and Harrison 1996).…”

Geophysical and Geotechnical Investigations of a Landslide in Kekem Area, Western Cameroon

“…Widespread 630 -660 Ma-old calc-alkaline granitoids, presently orthogneissified, result from a major episode of crustal accretion. A Paleoproterozoic crustal source in this region is attested by the presence of 2-Ga old inherited zircons in the granitoids [27].…”